1. Field of the Invention
This invention relates to flexible film laminates and packaging and, in particular, retortable pouches for food manufactured therefrom.
2. Description of the Prior Art
Metals and plastics coated with partially hydrolyzed ethylene-vinyl acetate copolymers are well known. U.S. Pat. No. 2,490,550 describes the use of partially hydrolyzed ethylene-vinyl acetate copolymers as a heat sealing composition for use on flexible sheet materials such as paper, metal foil, regenerated cellulose film, cellulose acetate, ethyl cellulose and other transparent films. U.S. Pat. No. 3,382,092 describes metallic plate protectively coated with a hydrolyzed ethylene-vinyl acetate copolymer. According to U.S. Pat. No. 3,549,727, both the vinyl ester content of an ethylene-vinyl ester copolymer and the degree to which the copolymer is hydrolyzed influence the lap-shear and peel properties of the hydrolyzed resin. The hydrolyzed resins described therein are said to be useful for bonding polymeric films, metal foils, leather, cellulosic surfaces, etc. The product of this patent is an adhesive composition based on a blend of a hydrocarbon resin polymer and an ethylene-vinyl ester copolymer which has been hydrolyzed to at least 60 mole percent and which, prior to hydrolysis, contained about 5-25 mole percent copolymerized vinyl ester and about 75-95 mole percent copolymerized ethylene. U.S. Pat. No. 3,562,234 teaches the use of a partially hydrolyzed ethylene-vinyl acetate copolymer as a heat-sealing material for textiles, as an adhesive for bonding paper, wood and plastics and as a coating for articles, in particular, of metal. U.S. Pat. No. 3,585,177 discloses the use of a partially hydrolyzed ethylene-vinyl acetate copolymer as a barrier coating applied to such substrates as paper, corrugated board, laminated paper products, polymer films and related materials. Similarly, in accordance with U.S. Pat. No. 2,595,740, a partially hydrolyzed ethylene-vinyl acetate copolymer is applied as a barrier coating to a base thermoplastic resin such as polyolefin, polyester, polyamide, and the like, employing as a bonding agent an ethylene polymer or copolymer. U.S. Pat. No. 3,616,191 recites a method for obtaining improved adhesion of extruded olefin polymer coating materials to packaging material substrates wherein a partially hydrolyzed copolymer of an olefin and an ester of an unsaturated alcohol, such as partially hydrolyzed ethylene-vinyl acetate, is used as an adhesion improving primer coat. U.S. Pat. No. 4,058,647 sets forth a process for preparing a laminated resin product having high gas-barrier capability wherein a two layer laminate is formed without the aid of an adhesive composition. The layers of the laminate comprise (1) a modified polyolefin composition and (2) a gas-barrier resin layer selected from the group consisting of a polyamide, a thermoplastic polyester and a hydrolyzed ethylene vinyl acetate copolymer. U.K. Pat. No. 1,510,115 describes a laminate film useful as a backing board film in vacuum packaging comprising a substrate layer of polyethylene, polypropylene or polyamide; an oxygen barrier layer of at least 85% hydrolyzed ethylene-vinyl acetate and a heat sealable layer of a blend of ethylene-vinyl acetate and a wax. Finally, U.S. Pat. No. 4,135,026 discloses the use of partially alcoholyzed ethylene-vinyl acetate copolymer as a red meat film wrap.